What causes "RegExp type cannot be serialized" in prestodb/presto?

Do not select or store REGEXP-typed values; use them only as arguments to like/regexp functions

prestodb/presto · error · PrestoException

GENERIC_INTERNAL_ERROR

GENERIC_INTERNAL_ERROR

Error message

RegExp type cannot be serialized

What it means

JoniRegexpType represents compiled regular expressions used internally by LIKE and regexp functions. Compiled regex objects have no serializable block representation, so createBlockBuilder always throws GENERIC_INTERNAL_ERROR with 'RegExp type cannot be serialized'. Reaching this means the engine attempted to materialize or store a REGEXP-typed value, which is unsupported.

Source

Thrown at presto-main-base/src/main/java/com/facebook/presto/type/JoniRegexpType.java:53

        super(new TypeSignature(NAME), Regex.class);
    }

    @Override
    public Object getObjectValue(SqlFunctionProperties properties, Block block, int position)
    {
        throw new UnsupportedOperationException();
    }

    @Override
    public void appendTo(Block block, int position, BlockBuilder blockBuilder)
    {
        throw new UnsupportedOperationException();
    }

    @Override
    public BlockBuilder createBlockBuilder(BlockBuilderStatus blockBuilderStatus, int expectedEntries, int expectedBytesPerEntry)
    {
        throw new PrestoException(GENERIC_INTERNAL_ERROR, "RegExp type cannot be serialized");
    }

    @Override
    public BlockBuilder createBlockBuilder(BlockBuilderStatus blockBuilderStatus, int expectedEntries)
    {
        throw new PrestoException(GENERIC_INTERNAL_ERROR, "RegExp type cannot be serialized");
    }
}

View on GitHub (pinned to 55bb57d202)

Solutions

Do not select or store REGEXP-typed values; use them only as arguments to like/regexp functions
Cast or restructure the query so the regexp is created inline (e.g. inside like()) instead of materialized
If a plugin function returns REGEXP, change it to return VARCHAR

Example fix

// before
SELECT like('abc', REGEXP_LIKE_PATTERN('a.*')) -- trying to materialize a regexp value
// after
SELECT like('abc', 'a.*') -- pattern supplied inline as varchar

Defensive patterns

Strategy: validation

Validate before calling

// Do not surface REGEXP-typed expressions in output/storage positions
// SQL guard: check the expression type before selecting
// DESCRIBE SELECT <expr>; -- must not show regexp in output columns

Try / catch

try {
    return blockBuilderCreation(type);
} catch (PrestoException e) {
    // GENERIC_INTERNAL_ERROR: opaque type (regexp/jsonpath) cannot be materialized
    // rewrite query to keep the value inline in function arguments
    throw e;
}

Prevention

Never SELECT, GROUP BY, or store REGEXP-typed values
Create regexp patterns inline within like()/regexp functions
Have custom functions return VARCHAR, not REGEXP

When it happens

Trigger: Any execution path that calls createBlockBuilder on JoniRegexpType, e.g. attempting to output, store, group by, or serialize a REGEXP value (a value of the internal regexp type) in a result set or exchange.

Common situations: Queries that try to SELECT a regexp constant or pass regexp values through connectors/JDBC; custom functions returning REGEXP; engine/plugin code that wrongly treats REGEXP as a storable type.

Related errors

AI-assisted analysis of prestodb/presto@55bb57d202 (2026-09-04). Data as JSON: /api/errors/7f3a8ef45f671caf. Report an issue: GitHub.